The document discusses modal verbs related to suggestion, advice, obligation, prohibition, and lack of necessity. It explains the use of various modal verbs such as 'ought to,' 'had better,' 'must,' 'have to,' 'can’t,' and 'mustn’t,' highlighting their nuances in expressing obligation and prohibition. Additionally, it covers expressions of lack of necessity like 'don’t have to,' 'don't need to,' and 'needn't.'

1. MODAL VERBS
S U G G E S T I O N A N D A D V I C E
O B L I G A T I O N A N D P R O H I B I T I O N
L A C K O F O B L I G A T I O N / N E C E S S I T Y

2. SUGGESTION AND ADVICE
Should
• General advice
• The most common modal verb
Ought to
• More formal than should
• Not used in questions and rarely in negatives.
Had better
• It is common when making a stronger suggestion.
• It is not used in questions

4. Suggestion and Advice Scale
Stronger suggestion/advice
Weaker suggestion/advice
Had better
Ought to
Should

5. OBLIGATION
Must
It shows us that the
obligation comes from the
speaker. It isn’t a law or a
rule.
• I must call my dad tonight.
Have to
It shows us that the
obligation comes from
somebody else. It’s a law
or a rule and the speaker
can’t change it.
• John can’t come because he has
to work tomorrow.

7. PROHIBITION
Both can’t and mustn’t are used to show that something is prohibited – it is
not allowed.
Can’t tells us
that something
is against the
rules.
Mustn’t mean
s that we are
not allowed to
do something.
It is prohibited.

9. LACK OF NECESSITY/OBLIGATION
"Lack of necessity" is also called "absence of obligation".
Don’t have to
• She doesn’t have to come today.
don't need to.
• She doesn’t need to come today.
needn't
• She needn’t come today.
You can do
something
if you want
to but it’s
not
compulsor
y.